<template>
    <div class="pagination">
        <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">上一页</button>
        <button v-if="startisShow" @click="$emit('getPageNo', 1)">1</button>
        <button v-if="startNumAndEndNum.start > 2">···</button>

        <!-- 中间部分 -->
        <button :class="{ active: page == pageNo }" v-for="(page, index) in startArr" :key="index"
            @click="$emit('getPageNo', page)">{{
                    page
            }}</button>


        <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
        <button v-if="endisShow" @click="$emit('getPageNo', totalPage)" >{{ totalPage }}</button>
        <button :disabled="startNumAndEndNum.end == totalPage" @click="$emit('getPageNo', pageNo + 1)" >下一页</button>

        <button style="margin-left: 30px">共 {{ total }} 条</button>
    </div>
</template>

<script>
export default {
    name: "Pagination",
    props: ['pageNo', 'pageSize', 'total', 'continues'],
    computed: {
        // 计算出总共有多少页
        totalPage() {
            // 向上取整
            return Math.ceil(this.total / this.pageSize);
        },
        // 计算出连续的页面的起始数组与结束数字[连续页码的数字：至少是5]
        startNumAndEndNum() {
            const { continues, pageNo, totalPage } = this;
            // 先定义两变量存储起始数字与结束数字
            let start = 0, end = 0;
            // 连续页码数字5【就是至少五页】，如果出现不正常的现象【就是不够5五页】
            if (continues > totalPage) {
                // 不正常的现象【总页数没有连续页码多】
                start = 1;
                end = totalPage;
            } else {
                // 正常现象【连续页码5，但是你的总页数一定是大于连续页码数的】
                // 起始数字
                start = pageNo - parseInt(continues / 2);
                // 结束数字
                end = pageNo + parseInt(continues / 2);
                // 把出现不正常的现象【start数字出现0|负数】纠正
                if (start < 1) {
                    start = 1
                    end = continues;
                }
                // 把出现不正常的现象【end数字大于总页码】纠正
                if (end > totalPage) {
                    start = totalPage - continues + 1;
                    end = totalPage;
                }
            }
            return { start, end }
        },
        startArr() {
            let startArr = [];
            let i = this.startNumAndEndNum.start;
            for (; i <= this.startNumAndEndNum.end; i++) {
                startArr.push(i)
            }
            return startArr;
        },
        startisShow() {
            return this.startNumAndEndNum.start == 1 ? false : true
        },
        endisShow() {
            return this.startNumAndEndNum.end == this.totalPage ? false : true
        }
    },
    methods: {
    }
}
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;

    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
</style>